The prior art includes steering devices for vehicles having a steering shaft by means of which the driver specifies a desired steering angle, having a steering gear, in which the steering shaft movement is transmitted via a pinion to a rack to control the rotatable wheels, and having an electric servo motor for steering assistance. To determine the steering torque which the driver is applying to the steering shaft, use is made of a sensor arrangement with a torque measuring unit, by means of which a relative rotation between two shaft sections of the steering shaft is determined. A steering device of this kind is known from DE 10 2007 032 907 A1, for example.
The steering shaft is rotatably mounted, wherein, owing to the vehicle movement, the bearings are subject to high loads, which lead to the development of noise and to impaired steering behavior in the case where there is bearing play.
It is the underlying object of the disclosure to improve the development of noise and the steering behavior in a steering device by simple design measures.
This object is achieved by means of this disclosure. The claims, description, and drawings describe expedient developments.
The bearing assembly according to the disclosure is used to bear a steering shaft or a shaft section, coupled to the steering shaft in terms of rotation, of a steering device for a vehicle. By way of the steering shaft, the driver specifies a steering torque and a steering angle, which is transmitted via a steering gear to a steering rack to control the rotatable wheels. The steering shaft is rotatably mounted in the bearing assembly and, for this purpose, the bearing assembly has at least one bearing in a bearing housing. In the bearing housing there is furthermore a damping disk, into which the bearing is integrated and which is supported radially by means of its circumferential side on the housing inner wall of the bearing housing, wherein one housing section is supported in the axial direction on the damping disk.
The damping disk thus has a dual damping function: on the one hand in the radial direction and, on the other hand, in the axial direction. In the radial direction, the damping disk, which accommodates the bearing, supports the steering shaft on the housing inner wall and thus stabilizes the steering shaft. In the axial direction, support takes place between a first housing section of the bearing housing and the damping disk, which is accommodated in a second housing section of the bearing housing. The two housing sections of the bearing housing can, if appropriate, form an axial movement relative to one another, which can be of the order of the housing clearance which usually occurs. Owing to the axial support of the housing section on the damping disk, shocks and impacts, one component of which acts in the axial direction of the steering shaft, are damped in an effective manner, for example.
The housing section supported axially on the damping disk is, for example, a housing cover, which rests on a pot-shaped main housing and is situated on the side facing away from the steering gear in the installed position. If the vehicle is subject to appropriate excitation in relation to the axial direction of the steering shaft, a component in the vehicle or the steering device, which component is in contact with the housing cover or the housing base body, can exert an impulse on the relevant housing section, and this impulse is damped by means of the damping disk.
The housing section which is supported axially on the damping disk can be supported either directly or indirectly—via another component, e.g. a spring element—on the damping disk. Via the spring element, force spikes during an impact excitation in the axial direction are avoided or at least reduced. The spring element is embodied as a wave spring, a diaphragm spring, a spiral spring or in some other way as a spring element, for example. The damping disk and the spring element can be embodied either as a coherent one-piece assembly module or as two individual parts.
According to an advantageous embodiment, the damping disk is composed at least partially of a vibration- and impulse-damping material. According to a preferred embodiment, the damping disk has an inner disk composed of harder material and an outer ring composed of softer material, which is supported on the inside of the housing and is connected to the inner disk. The outer ring is mounted on the circumferential side of the inner disk, being molded directly onto the inner disk, for example.
The inner disk is composed of a hard component, e.g. steel, aluminum, fiber-reinforced plastic or the like, and accommodates the bearing. The outer ring forms the soft component and is mounted as an O-ring, rubber mat, felt or injection-molded soft plastic, for example, on the circumference of the inner disk. According to an advantageous embodiment, the damping disk is embodied as a two-component plastic disk, where the inner disk is made from a fiber-reinforced hard component and the outer ring is embodied as an integrated soft component molded directly onto the circumference.
The spring element via which a housing section is supported on the damping disk preferably engages on the inner disk, composed of harder material, of the damping disk. The damping effect in the axial direction arises from the fact that the damping disk rests on the housing inner wall of one housing section with an ability for axial relative movement at least of the order of a bearing play, thus allowing the damping disk to move slightly axially relative to the housing section when subject to an axial impulse. In the embodiment of the damping disk with a harder inner disk and a softer outer ring, the outer ring is in direct contact with the housing inner wall, wherein a relative movement generally takes place in the material of the softer outer ring.
According to another expedient embodiment, the bearing integrated into the damping disk is designed as a floating bearing, in which the steering shaft or the shaft section is supported in the radial direction but is accommodated movably in the axial direction. According to another expedient embodiment, there is a second bearing in the bearing assembly, said bearing being integrated into the bearing housing at an axial distance from the first bearing. The second bearing is advantageously designed as a fixed bearing with radial and axial guidance of the shaft. Between the first and the second bearing, it is possible to arrange a helical gear, which meshes with a servo unit, in particular an electric servo motor. The servo torque generated by the servo unit is introduced into the steering shaft via the helical gear. The arrangement of the helical gear axially between the first bearing or damping disk and the second bearing allows compact embodiment of the bearing assembly.
The bearing assembly is part of the steering device for a vehicle and is arranged axially between the steering gear and the manual steering device to be actuated by the driver.